cred scan for provider block

[teowa]

enhance #83

armstrong credscan [-v] [-working-dir <path to Terraform configuration files>] [-swagger-repo <path/dir to the swagger files>]

option -swagger is changed to -swagger-repo to differentiate the -swagger used in armstrong test command which requires specific json file.

cred scan for azurerm and azapi provider block and scanning below secret properties, firing error if secret is plain text or the referenced variable has a default or not explicitly set sensitive=true:

• auxiliary_tenant_ids
• client_certificate
• client_certificate_password
• client_id
• client_secret
• oidc_request_token
• oidc_token
• subscription_id
• tenant_id

the errors are saved in json/markdown format file, the json is like:

{
    "file_name": "/Users/wt/projects/go/armstrong/hcl/testdata/test.tf",
    "name": "azurerm",
    "type": "provider",
    "property_name": "client_id",
    "error_message": "must use variable for secret field",
    "line_number": 9
  }

[ms-henglu]

Thanks for the PR! LGTM